320 FRANCIS RAMALEY 



parry i, Artemisia frigida, Potentilla concinna, P. hippiana, and 

 Achillea lanulosa. 



c. Short-grass Association. As frequently described (1, 2, 8, 

 9) the short grass of the plains is a well-marked association in 

 which the chief species are buffalo grass (Bulbilis dactyloides) and 

 grama grass (Bouteloua gracilis). The former species is more 

 abundant in fine-grained, the latter on slightly coarser soils. 

 As a rule the two occur as separate consociations. In our present 

 area of study the Bouteloua consociation is established in many 

 places on level or slightly sloping soil. No Bulbilis seems to be 

 present; perhaps the climate is too severe. But there are other 

 short grasses of like ecological import which grow in patches 

 much after the fashion of Bouteloua and Bulbilis. These are 

 Muhlenberbia richardsonis, Muhlenbergia cuspidata, and Distich- 

 lis spicata. They form rather denser growths, where they occur, 

 than the grama grass. 



Short grasses replace Agropyron in typical succession. They 

 become established most often as small clumps on patches of 

 ground bounded by shallow rain-cut channels and hence not 

 subject to over wash by sand. 



Within the clumps of short grass there are very few subordi- 

 nate plants, but a meter quadrat may contain relict individuals of 

 Chrysothamnus or Agropyron, not usually interspersed with the 

 short grass but forming patches alternating with it. A number of 

 meter quadrats have been examined by the writer and the area 

 covered by each species estimated as in previous studies (4). 

 Three of these records may be given as indicating common con- 

 ditions. The large percentage of bare ground is, of course, to be 

 expected in such sterile soil. 



Quadrat 3; short grass 



Bare ground 65 



Bouteloua gracilis 18 



Chrysothamnus linifolius 10 



Artemisia frigida 3 



Agropyron smithii 2 



Antennaria arida 1 



Tithymalus robustus 1 



100 



